- Synthesis of furo[2,3-d]pyridazin-4(5h)-one and its N(5)-substituted derivatives
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We report the efficient preparation of furo[2,3-d]pyridazin-4(5H)-one and its N-substituted derivatives starting from methyl 2-methylfuran-3-carboxylate. The Me group was converted to the aldehyde group, which was then condensed with hydrazine derivatives
- Karahan, Emrah,Koza, Gani,Balci, Metin
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- Twelve pregnane glycosides from Cynanchum atratum
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Eleven new 14,15-seco-pregnane-type steroidal glycosides, cynanosides P1-P5, Q1-Q3, R1-R3, and a novel 12,13-seco-14,18-nor-pregnane-type steroidal glycoside, cynanoside S, were isolated fr
- Bai, Hong,Li, Wei,Asada, Yoshihisa,Satou, Tadaaki,Wang, Yuanshu,Koike, Kazuo
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- Synthesis of Furans and Pyrroles from 2-Alkoxy-2,3-dihydrofurans Through a Nucleophilic Substitution-Triggered Heteroaromatization
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An effective method to synthesize α-functionalized furan and pyrrole derivatives was developed using 2-alkoxy-2,3-dihydrofurans as modular precursors. This protocol featured a previously unreported tandem nucleophilic substitution/heteroaromatization reaction. Nucleophiles such as indole, α-oxoketene dithioacetal, trimethoxybenzene, and dimethoxynaphthalene can react readily with 2-alkoxy-2,3-dihydrofurans to afford α-functionalized five-membered ring heterocycles in the presence of acid catalysts, such as copper bromide and iron chloride. The mechanism of the reaction was also discussed, in which the first step, nucleophilic substitution, is the key in triggering the succeeding heteroaromatization. This method can also be extended to the synthesis of dihydrothiophenes.
- Liu, Changhui,Zhou, Li,Huang, Wenbo,Wang, Man,Gu, Yanlong
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- Rhodium-catalyzed synthesis of 2,3 – Disubstituted N-methoxy pyrroles and furans via [3+2] cycloaddition between metal carbenoids and activated olefins
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For the first time, we report the synthesis of 2-substituted N-alkoxy pyrrole 3-carboxylate and furan 3-carboxylate via Rh-catalyzed [3+2] cycloaddition between α-diazo oxime ether or α-diazo carbonyl compounds with vinyl equivalents in a one-pot process. We have demonstrated ethyl vinyl ether as well as vinyl acetate as vinyl equivalents and both were found to give excellent yields. We have also demonstrated the synthesis of N-alkoxy dihydropyrrole derivatives by carrying out the reaction at low temperature.
- Kuruba, Bharath Kumar,Vasanthkumar, Samuel,Emmanuvel, Lourdusamy
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p. 3093 - 3098
(2017/05/08)
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- A metathesis approach to aromatic heterocycles
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The ring closing metathesis (RCM) reaction can be used to prepare substituted furans and pyrroles. By utilising a Pd-catalysed coupling reaction with methoxyallene, allylic alcohols and sulfonamides can be converted into substrates that are ideal precursors to ring closing metathesis. After the RCM reaction is complete, the addition of acid promotes an elimination of methanol to form the fully aromatised system. A range of different substitution patterns and functional groups are compatible with this sequence. Double allene coupling, RCM and elimination reactions are also possible and allow the formation of biaryl systems. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Donohoe, Timothy J.,Orr, Allan J.,Gosby, Katherine,Bingham, Matilda
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p. 1969 - 1971
(2007/10/03)
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- N-3-Substituted Pyrimidones as Potent, Orally Active, AT1 Selective Angiotensin II Receptor Antagonists
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A novel series of nonpeptide angiotensin II (A II) antagonists containing a pyrimidinone ring which carries a C-linked biphenyltetrazole moiety and a carboxyheteroaryl group on the 3-position have been prepared.Their affinity for the AT1 receptor was determined in a binding assay on rat adrenal cortical membranes.The in vivo antihypertensive properties were tested by evaluating the inhibition of the pressor response to A II followed by iv and id administration.Extensive molecular modeling studies, including comparison of molecular electrostatic potential distributions, conformational analysis, and overlays on a computational pharmacophore model of A II, were used to evaluate structural parameters of the new compounds, in comparison to other known A II antagonists (e.g., DUP-753 and SKandF 108566).According to the modeling studies, the introduction of a (carboxyheteroaryl)methyl moiety at the 3-position of the pyrimidinone ring led to derivatives with increased potency.Methyl 2-methyl>-1-(6H)-pyrimidinyl>methyl>-3-thiophenecarboxylate (3k, LR-B/081), one of the most potent compounds in the series (Ki = 1.4 nM), exhibited a marked antihypertensive activity on oral administration to conscious renal hypertensive rats, with long duration of action.It was selected for clinical evaluation in the treatment of hypertension in man.
- Salimbeni, Aldo,Canevotti, Renato,Paleari, Fabio,Poma, Davide,Caliari, Saturnino,et al.
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p. 4806 - 4820
(2007/10/03)
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- Studies Dealing with the Excited-State Behavior of Substituted 8-Oxabicyclooct-6-en-2-ones
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A series of 8-oxabicyclooct-6-en-2-ones was prepared by the rhodium(II)-catalyzed cyclization-cycloaddition reaction of α-diazopentanedione with various alkynes.The photochemical behavior of these oxabicyclic enones was investigated.Both direct and sensitized photolysis cleanly results in a 1,3-acyl shift.A slower, secondary photoprocess involving intramolecular hydrogen atom transfer and intramolecular cycloaddition of the resulting ketene was also uncovered.The photobehavior of the closely related 9-oxabenzocycloheptene system was also examined.The initially formed 1,3-sigmatropic rearranged product was found to undergo a novel 1,4-methoxyl migration on extended photolysis.The photochemistry of the homologous 7-oxabicyclohepten-2-one was studied.The results obtained can be interpreted in terms of an initial Norrish type I cleavage.The resulting diradical either couples to give the 1,3-acyl shift product or undergoes bond fragmentation, giving products derived from a stepwise retro-Diels-Alder reaction.
- Padwa, Albert,Zhi, Lin,Fryxell, Glen E.
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p. 1077 - 1083
(2007/10/02)
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- SYNTHESIS OF 3-ACYL AND 3-CARBOALKOXYFURANS BY THE CERIC AMMONIUM NITRATE PROMOTED ADDITION OF 1,3-DICARBONYL COMPOUNDS TO VINYLIC ACETATES
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3-Acyl- and 3-carboalkoxyfurans can be prepared in 30-55percent yield by the oxidative addition of 1,3-dicarbonyl compounds to vinylic acetates induced by ceric ammonium nitrate.
- Baciocchi, Enrico,Ruzziconi, Renzo
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p. 1841 - 1846
(2007/10/02)
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